(a) Technical Field
The present invention relates to diphenyl amine derivatives having luminescence property, and particularly to diphenyl amines substituted with various electron-donating or electron-withdrawing groups. The compounds of the present invention show blue or blue-green luminescence, and luminescence of the compounds herein can be achieved by UV or visible light, thus being useful as a fluorescent material or an organic electroluminescence device or display.
(b) Background Art
Electroluminescence, referred to as “EL” hereinafter, of organic materials was achieved by using anthracene single crystals in 1965 by W. Helfrich (W. Helfrich and W. G. Schreider, Phys. Rev. Lett., 1965. 14, 229) and M. Pope (M. Pope, H. Kallmann, J. Chem. Phys., 1965, 42, 2540) et al. However, little attention was drawn to this because luminescence efficiency was too low and a relatively high voltage was required. Since Tang (C. W. Tang, S. A. VanSlyke and C. H. Chen., J. Appl. Phys., 1989, 65, 3610) developed organic EL devices operable at a relatively low voltage and showing a high brightness in 1986, extensive researches have been exerted worldwide. Recently commercialized organic EL devices can be operated at a relatively low voltage and show a wide viewing angle and a prompt response.
To obtain an organic EL display with superior properties, the development of luminescence materials showing various colors such as blue, blue-green, red and orange is necessary. Tris(8-hydroxyquinoline)aluminum (‘Alq3’) is known as green luminescence material, which was developed in 1987 by Kodak. Other compounds such as quinacridone, coumarin derivatives, DPT and BDAC have also been developed. N,N′-bis(3-methylphenyl)-(1,1′-biphenyl)-4,4′-diamine (‘DPVBi’) and Alq3 have been developed as a blue luminescence. DCM2 and DCTTB have been developed by Kodak as a red luminescence material. Besides, rubrene and BTX have been developed as yellow and orange luminescence materials, respectively. The conventional red and blue luminescence materials are known to be problematic in luminescence yield and durability, respectively.